Joshua,
Well done for posting the yee olde bunker photos.
From expanding the photos, which admittedly does blur them a bit, some of the bunkers seem to be revetted, at least partially, eg 4th at Sandwich, Redan at NB.
The long thin, narrow snakey bunker at Sunningdale is interesting. Thin and narrow would give some interesting stances from which to play shots. Interesting lies too.
The sleeper wall on the left side of the first Rye photo is pretty high. A barrier anticipating more wind blown sand or that sleepers are extremely hard work to cut in half with a saw?
There are still sleepers sticking up vertically above ground at some UK courses, Aberdovey on the 4th and 16th holes being examples (plus those of the Dye family variety elsewhere).
Atb